Embodiments of this invention generally relate to elevator systems, and more particularly, to improving the safe operation of low pit or low overhead elevator systems by limiting movement of elevator cars and counterweights when respective hoistways are accessed.
Traditionally, elevator systems required hoistways with significant spaces below the bottom elevator landing, also known as pits, to allow access to maintenance personal and to house various components of the systems. Similarly, large overhead spaces were also required to allow a mechanic to service various components at the top of the hoistway from the top of an elevator car. Recently, elevator systems having either low pits and/or low overhead areas have become more common. Reducing the depth of the pit or the height of the overhead allows smaller hoistways to be used, thereby allowing for lower construction costs, more flexibility of design, and reduced impact on construction, among other benefits. However, low pit/low overhead elevator systems also present additional challenges. Low pit/low overhead systems are typically made possible by allowing elevator cars to come much closer to the top and/or bottom of the hoistways during normal operation. This creates a challenge when system components (drives, controllers, machines, brakes, etc.) located in the hoistway need to be serviced. According to most elevator codes, a minimum safe distance must be present between the top of the elevator car and the top of the hoistway when maintenance personnel are present in the hoistway. Similar requirements are present related to pit depth. In current low pit/low overhead elevator systems, these requirements have been addressed using separate devices to physically limit the travel of the cars in order to provide a safety refuge space for a person in the pit or on top of the car. While effective, the use of two separate devices can increase the cost of the overall system.